tracing: Add a helper function for event print functions

Move duplicate code in event print functions to a helper function.

This shrinks the size of the kernel by ~13K.

   text    data     bss     dec     hex filename
6596137 1743966 10138672        18478775        119f6b7 vmlinux.o.old
6583002 1743849 10138672        18465523        119c2f3 vmlinux.o.new

Link: http://lkml.kernel.org/r/51258746.2060304@huawei.com

Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

include/linux/ftrace_event.h

@@ -38,6 +38,12 @@ const char *ftrace_print_symbols_seq_u64(struct trace_seq *p,
 const char *ftrace_print_hex_seq(struct trace_seq *p,
 				 const unsigned char *buf, int len);
 
+struct trace_iterator;
+struct trace_event;
+
+int ftrace_raw_output_prep(struct trace_iterator *iter,
+			   struct trace_event *event);
+
 /*
  * The trace entry - the most basic unit of tracing. This is what
  * is printed in the end as a single line in the trace output, such as:
@@ -95,8 +101,6 @@ enum trace_iter_flags {
 };
 
 
-struct trace_event;
-
 typedef enum print_line_t (*trace_print_func)(struct trace_iterator *iter,
 				      int flags, struct trace_event *event);
 

include/trace/ftrace.h

@@ -227,29 +227,18 @@ static notrace enum print_line_t					\
 ftrace_raw_output_##call(struct trace_iterator *iter, int flags,	\
 			 struct trace_event *trace_event)		\
 {									\
-	struct ftrace_event_call *event;				\
 	struct trace_seq *s = &iter->seq;				\
+	struct trace_seq __maybe_unused *p = &iter->tmp_seq;		\
 	struct ftrace_raw_##call *field;				\
-	struct trace_entry *entry;					\
-	struct trace_seq *p = &iter->tmp_seq;				\
 	int ret;							\
 									\
-	event = container_of(trace_event, struct ftrace_event_call,	\
-			     event);					\
-									\
-	entry = iter->ent;						\
+	field = (typeof(field))iter->ent;				\
 									\
-	if (entry->type != event->event.type) {				\
-		WARN_ON_ONCE(1);					\
-		return TRACE_TYPE_UNHANDLED;				\
-	}								\
-									\
-	field = (typeof(field))entry;					\
-									\
-	trace_seq_init(p);						\
-	ret = trace_seq_printf(s, "%s: ", event->name);			\
+	ret = ftrace_raw_output_prep(iter, trace_event);		\
 	if (ret)							\
-		ret = trace_seq_printf(s, print);			\
+		return ret;						\
+									\
+	ret = trace_seq_printf(s, print);				\
 	if (!ret)							\
 		return TRACE_TYPE_PARTIAL_LINE;				\
 									\

kernel/trace/trace_output.c

@@ -397,6 +397,32 @@ ftrace_print_hex_seq(struct trace_seq *p, const unsigned char *buf, int buf_len)
 }
 EXPORT_SYMBOL(ftrace_print_hex_seq);
 
+int ftrace_raw_output_prep(struct trace_iterator *iter,
+			   struct trace_event *trace_event)
+{
+	struct ftrace_event_call *event;
+	struct trace_seq *s = &iter->seq;
+	struct trace_seq *p = &iter->tmp_seq;
+	struct trace_entry *entry;
+	int ret;
+
+	event = container_of(trace_event, struct ftrace_event_call, event);
+	entry = iter->ent;
+
+	if (entry->type != event->event.type) {
+		WARN_ON_ONCE(1);
+		return TRACE_TYPE_UNHANDLED;
+	}
+
+	trace_seq_init(p);
+	ret = trace_seq_printf(s, "%s: ", event->name);
+	if (!ret)
+		return TRACE_TYPE_PARTIAL_LINE;
+
+	return 0;
+}
+EXPORT_SYMBOL(ftrace_raw_output_prep);
+
 #ifdef CONFIG_KRETPROBES
 static inline const char *kretprobed(const char *name)
 {